Known automation systems typically comprise a higher-level controller, for example, in the form of a stored program controller (abbreviated as SPC) that can communicate through a field bus system with input/output devices, also called IO devices. The IO devices preferably involve sensors and actuators. For some time now, a special link system, specifically, the IO link communication system, has been used to intelligently link IO devices to an automation system. This standardized IO link communication system includes an IO link master to which multiple IO link devices, as they are called in the IO link standard, are connected in a star topology. The IO link communication system is consequently called a point-to-point communication system. In this type of IO link communication system, the IO link devices can be addressed synchronously, i.e., simultaneously by the IO link master. The communication between the IO link master and the IO link devices connected thereto is preferably effected only in response to a request from the IO link master. Here a differentiation is made between cyclic and acyclic data communications. Process data are transmitted cyclically in data frames. Service data are transmitted acyclically from the IO link devices to the IO link master in response to a request of the IO link master. Finally, the IO link devices communicate through the IO link master with the higher-level control means of the automation system.
It is necessary that the higher-level control means knows precisely when an IO link sensor acquires measurement data, or an IO link actuator performs an action, in order to be able to control and monitor a process sequence in an error-free manner.